I have a few questions that I'm not sure on how to do: 1) A 20kg mass is connected to a 8kg mass by a thin frictionless string on a pulley. It accelerates to 1.5m/s2 and the heavier mass slides along a rough surface. What is the coefficient of friction? 3) 1.00g of U-238 fuel is consumed. Assuming 100% efficiency, what is the nuclear energy used in joules? 4) A 7.5x10^3kg sattelite orbits a planet at an altitude of 300km. The radius of the planet is 8.5x10^6. The gravitational field at the radius is 6.5N/kg. What is the mass of the planet? 5)A rocket car uniformly accelterates at 15m/s2 and heads towards a cliff that is 75m high. At what distance should the landing pad be placed so the car can land? Need help with these questions ASAP.. Thanks.